Abstract. In teacher education, a key issue is how prospective teachers learn. At the University of Lisbon, based on an inquiry-based approach to mathematics learning, we developed a secondary school mathematics teacher education program, in which a central feature is the elaboration of a final investigative report based on teaching practice. In this paper, our aim is to understand the professional learning opportunities and difficulties recognized by prospective teachers (PT) in their final reports, by addressing the following research questions: (i) What didactical choices do PT mention regarding the approach to teaching, the use of tasks, resources and assessment strategies in their teaching practices? (ii) What transversal elements of teaching practices do they recognize as enabling their professional development? and (iii) What elements of the investigative work do PT refer to as major professional learning outcomes? Using content analysis, we reviewed, coded, and analyzed all 38 reports produced so far in the program. The results suggest that the PT embraced an inquiry-based approach to learning, valuing the role of suitable tasks and of whole class discussions. They also valued reflection and collaboration as practices that support professional development. Prospective teachers also indicated some difficulties and challenges in doing this investigation based on their teaching practice, but even so they tended to regard it a learning opportunity. We conclude that the final report, by its content, structure, and working processes as framed in this teaching education program, supports participants' development as teachers who hold research in positive regard.